1. Field
The present disclosure generally relates to integrated circuit (IC) packages and, more particularly, to methods of plating and singulating IC packages.
2. Description of the Related Art
The silicon chips on which integrated circuits are formed are so small that they are sensitive to damage and hard to handle, and many IC chips are packaged in enclosures that protect the chips and provide larger contact leads that can be attached to circuitry on substrates such as printed circuit boards (PCBs). One common method of assembling an IC package of this type is to attach a “leadframe” as a mechanical support to the die during its assembly. A portion of the leadframe is trimmed off, leaving only the leads that provide the external connections for the finished product. A leadframe comprises a “die attach pad”, to which the die is attached, and “leads”, which provide external electrical connections. The die, adhesive, wires and leadframe are encased in a housing that may be a molded plastic part or an overmold of a mold compound, wherein the terminal are exposed on the exterior surface of the housing.
In certain configurations of IC packages, such as a Dual Flat No-lead (DFN) or Quad Flat No-lead (QFN) package, the terminals are exposed on the underside of the IC package. FIGS. 1A and 1B depict a typical IC package having terminals that do not protrude from the housing but, rather, are exposed on the underside and side of the IC package, wherein FIG. 1A is a view of the top and FIG. 1B is a view of the bottom of the same IC package. This configuration of IC package is compact and minimizes the area required to mount the IC package on a PCB. One difficulty with this type of package is that it is not possible to visually inspect the solder joint between the terminals and the contact pads of the PCB. Inspection of the solder joints of this type of IC package must be performed using X-ray images.
It has been found that the creation of a notch at the outside lower corner of the terminal produces a solder fillet when a good solder joint has been created. It is possible to inspect this solder fillet in place of X-raying the solder joint to verify that a good solder joint has been formed. Elimination of the X-ray inspection may reduce the cost and complexity of the product line as well as increasing the production rate. Creation of a notch by saw cutting is disclosed in U.S. Pat. No. 6,608,366 to Fogelson et al. The disclosed process requires a first half-thickness saw cut to create a notch, and a second thinner saw cut to singulate the IC packages. Saw blades are a significant expense in the manufacturing of IC packages and the need to perform the half-thickness saw cut prior to singulation adds cost to the manufacturing process.